The present invention relates generally to sealed containers for holding liquids under pressure, and more specifically to a compound plastic container formed from a single blow molded plastic body for holding pressurized beverages such as beer and soft drinks.
Containers constructed from thermoplastic material have become widely used in the beverage industry, competing with traditional metal and glass containers. Attractive features of plastic containers include resistance to rupture; transparency, allowing viewing of the bottled contents; light weight, reducing shipping costs, and relatively low manufacturing costs. However, the low manufacturing cost benefit of thermoplastic containers is only realized when the container walls are of a relatively thin construction. Plastic containers with thick walls are relatively expensive because the cost of plastic per pound is greater than the cost of glass.
Thin wall construction has been the source of a number of problems. Under pressure, the cylindrical sidewall of a plastic container tends to expand, especially at the mid portion of the sidewall. Thus, if extremely thin wall containers are used, a bulging area at a mid portion of the sidewall is produced. Even if such a container is capable of holding pressurized contents without rupture, a bulging configuration is aesthetically unacceptable from a marketing standpoint. The bottomwall of a cylindrical container also tends to expand outwardly and assumes a convex configuration which causes the container to be unstable when placed on a flat surface. One manner of resolving this problem with the bottom wall is to substantially increase its thickness or to provide a container having a deeply recessed concave bottomwall. Both of these solutions have, for the most part, not been implemented due to the expense of providing such bottomwall configurations. Another solution which has been widely used in the industry, is to provide the container with a separate support base which is mounted at the bottom of the container to enclose the rounded bottomwall and provide a separate bottom surface capable of supporting the container. Such containers, sometimes referred to as composite containers, contain relatively less plastic material than a container having a single thick bottomwall portion and are thus less expensive to produce. Compound plastic containers have thus gained a general acceptance in the industry.
The convex bottomwall portion of a container body provided with such a base cup may be relatively thin walled with respect to the cylindrical sidewall portion of the container body due to the fact that a convex or hemispherical wall configuration is inherently stronger than the cylindrical configuration of the sidewall and also due to the fact that additional strength may be provided to the bottom portion by the surrounding base cup. However, it is generally desirable to provide a relatively high-strength base cup since this portion of the container is most likely to be subjected to shocks.
In conventional blow forming techniques used to produce such a composite container, it is conventional to provide one mold for the blow molded body portion of the container and to provide a second mold to produce the base cup portion of the container. Each blow molded container and base cup, subsequent to blow molding, may be trimmed as necessary to remove any undesirable preform connection structure and are thereafter fixedly attached to one another by various attachment means.
Plastic containers and methods of forming and assembling plastic containers have been the subject of numerous patents.
Whitman U.S. Pat. No. 2,717,619 discloses a cylindrical container which may be made from blow molded polyethylene which has a generally cylindrical shape with a plurality of circumferential ribs at the outer surface thereof. The cup is provided with rib receiving recesses on the inner surface thereof may be slipped over the top of the container and sealed thereto with a wire band or the like. The container may be cut with the ribs to place the top thereof at the same level as the unused contents therein and the cup may thereafter be resealed over the newly formed top surface.
Thielfoldt U.S. Pat. No. 3,084,395 and Britten U.S. Pat. No. 3,187,381 disclose methods of blow molding hollow articles from plastic material.
Hunter U.S. Pat. No. 3,198,375 discloses a blow molded plastic container having a closure member formed integrally with the remainder of the container in the molding process and subsequently severed therefrom and introduced into a frictionally interlocking position to effect closure of the end opened by the severance after the container is filled with liquid.
Klygis U.S. Pat. No. 3,409,710 discloses a dual wall container formed from a hollow molded bottle by removing an upper portion of the neck of a container and applying it over the lower portion of the neck to seal the container.
Showalter et al. U.S. Pat. No. 3,632,717 discloses a container which may be made from a polyethylene composition which is centrifugally cast. After the casting step the molded product has no access opening, but has an outwardly projecting flange which is cut immediately adjacent a rib whereby the upper portion of the flange is removed to form an opening. The removed portion of the flange is again cut at another rib to form a dish shape cover which mates with the upper area of the previously cut rib at the mouth of the container. The device is closed by a channel shaped metal band which is expandable and contractable in diameter.
Doughty U.S. Pat. No. 3,726,429 discloses a composite package material for holding carbonated beverages which includes a thermoplastic container having a hemispherically shaped bottom section and a support for holding a container in an upright position which is formed from a thermoplastic compatible with the container. The support is heat sealed to the bottom section of the container.
Uhlig U.S. Pat. No. 3,949,034 discloses a container for retention of liquid under pressure formed from a blow molded plastic container having a bottom pressure wall which is formed during blowing by telescopically moving a bottom defining surface of the blow mold relative to the remainder of the blow mold.
Dodsworth et al. U.S. Pat. No. 3,978,232 discloses a thin walled container for pressurized liquids. An inner thin walled container is formed from high impact polystyrene. An outer restraining cup, made of high impact polystyrene and having a wall thickness which is greater than that of the inner container, engages at least an annular region of the container. The container has a gas impermeable liner such as BAREX 210, and acrylonitrile copolymer. The lid which seals the container may be aluminum of the pull ring type. The inner container is expanded by pressure of the sealed liquid whereby it engages the restraining cup which provides support and allows the container to be free standing so long as the carbonated beverage therein remains sealed. The cup is held to the inner container wall by frictional engagement and when the pressure in the inner container is released, the cup may be removed from a inner container and used as a drinking vessel.
Davis U.S. Pat. No. 4,127,430 disclosed a method of making a container having a blown plastic liner and method and apparatus for forming the same.
Jakobsen U.S. Pat. No. 4,293,359 discloses the use of a stabilizing foot supporting a plastic container at its lower end. Jakobsen teaches that various types of feet have been used in either parts projecting from the bottom of the bottle or separate parts fixed to the containers and that in the latter case these parts are applied to the container by snap engagement, riveting, or other methods. The type of plastic which can be used includes polyvinyl chloride (PVC) acetylonitrile (AN), and polyethylene terephthalate (PET).
Black U.S. Pat. No. 4,305,904 discloses a molding step in which the unwanted dome portion of the container is molded to have an engaging groove therein. The container is conveyed to a dome removal device which engages the groove in the dome, moves the dome against a cutting edge, and rotates the container to effectuate a complete removal of the dome. The method of removing a tail portion of the container is also disclosed. Both tail and dome removal operations are performed immediately after ejection of the containers from the molds while the plastic is still hot and pliable.
It is an object of the present invention to provide a composite thermoplastic container in a manner which eliminates one of the conventional blow forming steps used in producing such containers.
It is a further object of the invention to provide a thermoplastic container having a configuration capable of withstanding pressures associated with carbonated beverages such as beer and soft drinks.
It is another object of the invention to provide such a container configuration in an aesthetically pleasing shape.
It is another object of the invention to provide such a container using a minimal amount of thermoplastic material.
It is another object of the invention to provide such a container in a cylindrical can configuration.
It is another object of the invention to provide such a container with an inner lining structure.
It is another object of the invention to provide such a container without an inner liner structure.
It is another object of the invention to provide such a container in a transparent, translucent or opaque medium.